In a semiconductor device manufacturing process, a method has been known, which dry-etches a silicon oxide film existing in a surface of a semiconductor wafer (hereinafter referred to as “wafer”) without using plasma. Such a dry-etching method includes: a modification process in which a reaction product is generated by supplying a mixture gas including a hydrogen fluoride gas (HF) and an ammonia gas (NH3) into a chamber in which the wafer is received while controlling an interior of the chamber to have a low pressure close to a vacuum state and adjusting a temperature of the wafer to a predetermined temperature, thereby modifying the silicon oxide film; and a heating process in which the reaction product is heated so as to be vaporized (sublimated). The dry-etching method etches the silicon oxide film by modifying the surface of the silicon oxide film to the reaction product and removing the reaction product by heating (see Patent Documents 1 and 2).
The etching process described above is applied to, for example, a process for etching a sacrificial oxide film of a wafer W having a structure shown in FIG. 1. As shown in FIG. 1, in the wafer W, a HDP-SiO2 film 101, which is an interlayer insulating film, is formed on a surface of a Si layer 100. In a surface of the HDP-SiO2 film 101, a resist film 102 is formed. Moreover, in the HDP-SiO2 film 101, a groove H (e.g., a contact hole) is formed, and a sacrificial oxide film 103 is formed in a lower portion of the groove H. Further, a SiN film 104, which is an insulator, is formed in a side wall portion of the groove H.